The present invention relates to sample observation method and equipment intended to be used for an automatic method of closer inspection for a defect developed or a foreign material deposited during the production of semiconductors.
As a method of observing samples by which a foreign material or a defect can be viewed in detail, for example, the method described in JP-A-No. 09-139406 has been disclosed.
According to this method, an image pickup device such as a microscope moves to an area where a fault exists, based on the coordinates data obtained beforehand by a discrete fault inspection apparatus, and captures a defective sample image and then captures a magnified view of a foreign material or defect that is located by any means.
Although not clearly mentioned in the above-mentioned JP-A-No. 09-139406 regarding prior art, the above previous method has proved to have some drawbacks as the inventors of the present invention examined this publication. Its drawbacks are as follows:
Judging whether defect extraction processing is successful is possible only by viewing display images that have been acquired, when there is no means for the user to check the validity of the images. If the processing is unsuccessful, we cannot know how it failed. Consequently, the setup for capturing sample images in good conditions of executing the defect extraction takes time.
After a defective sample image including a foreign material or a defect is acquired, when locating the area of the foreign material or the defect or recognizing its shape on the defective sample image with the background pattern behind it, it is desirable to capture a reference sample image not including any fault on the same background pattern together with the defective sample image and compare both images.
When closer inspection is performed by magnifying the local area of the foreign material or defect, if the defective sample image is first captured as is in the above previous method (cited as an example), the stage (platform) on which a sample is placed for inspection must be moved after the first image of the sample is captured so that the area of the reference sample image will fall within the field of view of an image pickup device. After the second image is captured, the exact location of the foreign material or defect is calculated and then the stage must be moved again so that the fault location will fall within the field of view of the image pickup device. Thus, the stage would move frequently to be repositioned and it would take some time to acquire the images.
If the dimensions of the field of view of the microscope when capturing a defective sample image approximate to the stage positioning error, the positioning in an area on the same background as for the defective sample image is difficult and therefore a reference sample image is difficult to acquire.
If capturing a reference sample image corresponding to a defective sample image is always performed, the number of captured images increases in proportion to the number of defects and the time required for acquiring the images increases correspondingly.
An object of the present invention is to provide sample observation method and equipment that enable faster and efficient observation of a defect, solving the problems from the drawbacks involved in prior art.
In order to attain the above object, the present invention offers a method of observing samples in which a view of a desired area of a sample is captured and the thus acquired image is displayed on a first screen, an area to be magnified and observed within the image displayed on the first screen is superimposed on the display image, a magnified view of the displayed area to be magnified and observed within the sample is captured, and the thus acquired magnified image is displayed on a second screen.
In order to attain the above object, the present invention offers a method of observing samples in which the position of a sample is adjusted so that a desired area of the sample will fall within the field of view of observation means for observation, a view of the desired area of the sample is captured at first scale factor and thus a first image is acquired, the first image is displayed on a first screen, an area to be magnified and observed within the first image displayed on the first screen is superimposed on the same screen, a view of the area to be magnified and observed is captured at second scale factor that is larger than the first scale factor and thus a second image is acquired, and the second image is displayed on a second screen.
In order to attain the above object, furthermore, the present invention offers a method of observing samples by using a scanning electron microscope wherein the position of a sample is adjusted so that a desired area of the sample will fall within the field of view of the scanning electron microscope for observation, a view of the desired area of the sample is captured by the scanning electron microscope at first scale factor and a first image is thus acquired, this first image is displayed on a first screen, the first image displayed on the first screen is compared with a reference sample image, an area to be magnified and observed within the first image displayed on the first screen is determined, based on the above comparison, and a magnified image of the area thus determined to be magnified and observed is displayed on a second screen.
In order to attain the above object, furthermore, the present invention offers a method of observing samples characterized by: acquiring a reference sample image not including any defect on a sample by capturing an image of the sample, based on the information on a defect developed on the sample and detected by an inspection apparatus; acquiring a defective sample image including the defect on the sample by capturing an image of the sample, based on the information on the defect developed on the sample and detected by the inspection apparatus; locating the defect on this defective sample image by comparing the reference sample image and the defective sample image; capturing a magnified view of the local area where the located defect exists on the defective sample image, thus acquiring a magnified image of the defect; and displaying this magnified image of the defect on a screen.
In order to attain the above object, furthermore, the present invention offers a method of observing samples characterized by: acquiring a reference sample image not including any defect on a sample by capturing an image of the sample, based on the information on a defect developed go on the sample and detected by an inspection apparatus; adjusting the position of the sample so that the defect will fall within the field of view of image capture, based on the information on the defect developed on the sample and detected by the inspection apparatus; acquiring a defective sample image including the defect on the sample by capturing an image of the sample in the adjusted position; locating the defect on this defective sample image by comparing the reference sample image and the defective sample image; capturing a magnified view of the local area where the located defect exists within the field of view of image capture, thus acquiring a magnified image of the defect; and displaying this magnified image of the defect on a screen.
In order to attain the above object, furthermore the present invention offers a method of observing samples characterized by: acquiring a reference sample image not including any defect on a sample by capturing an image of the sample, based on the information on a defect developed on the sample and detected by an inspection apparatus; acquiring a defective sample image including the defect on the sample by capturing an image of the sample, based on the information on the defect developed on the sample and detected by the inspection apparatus; locating the defect by comparing the reference sample image and the defective sample image; capturing a magnified view of the local area where the located defect exists on the defective sample image, thus acquiring a magnified image of the defect; erasing the background from this magnified image of the defect; and displaying on a screen the magnified image of the defect from where the background has been erased.
In order to attain the above object moreover, the present invention offers an equipment for observing samples, configured to have: image pickup means to capture a view of a sample, thus acquiring an image of the sample; storage means to receive and store data about a desired area of the sample, the view of the area to be captured by the image pickup means, from the external; position control means to control the position of the sample toward the image pickup means, based on the data about the desired area of the sample stored into the storage means; display means to display images of the sample acquired by being captured by the image pickup means; and arithmetic control means to locate a defect on the sample by comparing a plurality of images of the sample zoomed-in by first scale factor and captured by the image pickup means after the sample is positioned by the position control means and make the display means display an image of the defect zoomed-in by second scale factor that is larger than the first scale factor, together with an image including the defect captured at the first scale factor.
In order to attain the above object, moreover, the present invention offers an equipment for observing samples, configured to have: storage means to receive and store the information on a defect developed on a sample acquired through inspection with an external defect inspection apparatus from the defect inspection apparatus; image pickup means to capture a view of the sample, thus acquiring an image of the sample; position control means to control the position of the sample, based on the information on the defect developed on the sample stored into the storage means; defect locating means to locate the defect by comparing an image of the sample not including the defect and an image of the sample including the defect, zoomed-in by first scale factor and captured by the image pickup means after the sample is positioned by the position control means, and display the image including the defect on a screen; and magnified defect display means to display a magnified image of the defect located by the defect locating means, the image captured by the image pickup means at second scale factor that is larger than the first scale factor.
In order to attain the above object, moreover, the present invention offers an equipment for observing samples, configured to have: image pickup means to capture a view of a sample, thus acquiring an image of the sample; position control means to control the position of the sample so that a defect on the sample will fall within the field of view of the image pickup means, based on the information on the defect on the sample acquired through inspection with an external defect inspection apparatus; defect locating means to locate the defect by comparing an image of the sample not including the defect and an image of the sample including the defect, zoomed-in by first scale factor and captured by the image pickup means after the sample is positioned by the position control means, and display on a screen the image of the sample including the thus located defect; and magnified defect display means to display a magnified image of the local area of the sample corresponding to the location of the defect on the image including the defect displayed on the screen of the defect locating means, the image captured by the image pickup means at second scale factor that is larger than the first scale factor.
By displaying a defective sample image on which the result of defect extraction processing is superimposed, the present invention enables the user to verify the validity of the defect extraction.
Processing sequence has been arranged so that the number of stage moves will decrease for more efficient image acquisition. Based on the information on the coordinates of a foreign material or defect, given in advance from a discrete inspection apparatus, a reference sample image corresponding to a defective sample image including the foreign material or defect image is initially acquired. Thereafter, the defective image of the foreign material or defect is captured.
Furthermore, the present invention captures images of samples scaled up by two different scale factors by capturing reference and defective sample images zoomed-in by a lower scale factor, a foreign material or defect is located. A view of the local area where the located foreign material or defect exists is captured, closed up by a higher scale factor. Thereafter, the stage is moved to a position for capturing a reference sample image corresponding to the defective sample image including the foreign material or defect and the reference sample image is captured at the lower scale factor. On the reference sample image of lower scale factor, a template of the area corresponding to the field of view set for image capture by higher scale factor is positioned. By centering the focus on the template area and closing up, a reference sample image of higher scale factor is captured. In this way, the present invention makes it possible that a reference sample image of higher, scale factor corresponding to a defective sample image of higher scale factor be acquired.
Acquired reference sample images are recorded in such a manner that a reference sample image and its area set for image capture, based on the system of coordinates on a chip, assigned for each individual chip, are recorded in a set. When another defect is inspected, if the area for capturing its reference sample image, expressed by coordinates on a chip, is found in the recorded areas of the acquired images, the recorded image is used instead of acquiring the reference sample image. By applying the present invention in this way, the efficiency of image acquisition and inspection would further increase.